A conventional inboard marine engine utilizes a cooling system in which seawater is drawn from the lake or other body of water and is circulated through the cooling system, and then discharged overboard. In a typical cooling system for V-6 inboard marine engine, seawater is drawn into the cooling system by a pickup pump, and is then directed to a thermostat housing, which contains a thermostat. When the thermostat is closed, a portion of the incoming water will be pumped by a circulating pump through outlets in the thermostat housing to the exhaust manifold and elbows of the engine, while a second portion of the incoming seawater is circulated through the engine block. As the temperature rises and the thermostat is opened, a portion of the returning water in the circulating system will flow to the exhaust manifolds, and then overboard in the exhaust of the engine.
When the engine is not operating, water will collect in certain portions of the cooling system, such as the exhaust manifold, the engine block and the circulating pump. If the ambient temperature drops below freezing for extended periods, the collected water can freeze, which can cause cracking of the engine block or other components of the engine. Because of this, it is customary to winterize the engine at the outset of cold weather. However, winterizing is a difficult and time consuming operation, but because of the potential danger of freezing, the marine engine is normally winterized well before the advent of freezing weather, thus substantially reducing the overall boating season.
The co-pending U.S. patent application Ser. No. 08/521,746 filed Aug. 31, 1995 and entitled Drain Valve for a Marine Engine, is directed to a drain valve assembly associated with an inboard marine engine for automatically draining water from the cooling system when the ambient temperature decreases below a preselected value, such as about 50.degree. F. The drain valve of the above mentioned patent application is connected via hoses or conduits to the exhaust manifolds of the engine, the circulating pump hose, and the engine block. When the ambient temperature falls below the preselected value, the drain valve will open, thus draining water from these portions of the engine to prevent freezing of the water and potential damage to the engine.
The seawater which is circulated through the cooling system of the marine engine contains debris, such as sand, dirt, and other particulate material. In order for the drain valve to function effectively, it is necessary to keep the debris away from the drain valve. Debris entering the valve members can prevent flow, or debris lodging between the valve members and the valve seats can cause leakage through the valve.